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A. JOHNSON WEAR SHOE FOR CAM FOLLOWER Filed March 3. 1952 FIG.5.

INVENTOR. ELDON A. JOHNSON ATTORNEY 2,733,618 a a WEAR SHOE FOR CAM FOLLOW R Eldon A. Johnson, St. Louis, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., acorporation of Delaware 1 j Application March a, 1952, Serial No. 274,592

7 Claims. 01. 74-569 This invention relates to cam follower mechanisms, particularly, of the type embodying a slidable shoe between'the cam and follower lever.

A mechanism of the above type, for operating a mechanical fuel 'pump which supplies fuel to an automotive engine, is illustrated in an applicatiomiSerial No. 236,408, filed July 12, 1951, in the name of James L. Edelen, now Patent No. 2,654,266 of October 6,1953. It has been found, however, that with the use of this mechanism, an annoying whistling sound is produced on occasion. Consequently, it is the main object of the present invention to improve upon the mechanism describedin the mentionedeo-pehding application in a mannerjto eliminate the whistle. The mentioned sound is believed to be caused by vibration between the shoe and lever due to chattering and rocking about central high points in the bearing surfaces. According to the present invention, the, objectionable noise is eliminated by reducing the frictional engagement between the shoe and lever, to eliminate chattering and, at the same time, restricting such engagement to runnerlike portions of the engaging surfaces at opposite sides of the longitudinal center line so that rocking vibration between the shoe and lever is eliminated without the necessity of carefully ground or lapped bearing surfaces.

In the accompanying drawing which illustrates the invention:

Fig. 1 is a side view of an automotive fuel pump embodying the invention, parts being broken away and sectioned.

Fig. 2 is an enlarged section showing the cam, slidable shoe, and the adjacent portion of the follower lever.

Fig. 3 is a bottom view of the slidable shoe, showing the lever engaging surface thereof.

Figs. 4 and 5 are transverse sections of Fig. 2, Fig. 5 also including the cam shaft.

Fig. 6 is a composite, transverse section, the left half corresponding, approximately, to Fig. 4 and the right half corresponding, approximately, to Fig. 5, but showing a modification.

The automotive fuel pump illustrated is of the well known Carter type now in wide use and includes a body portion 8 with an operating diaphragm, valves, and vapor dome spaces, all as clearly disclosed and claimed in a co-pending application Serial No. 728,979, filed February 17, 1947, in the name of Irven E. Coffey, now Patent No. 2,625,114. Secured to the upper part of the body 8 is a right angle lever'housing 9 into which projects diaphragm stem 10 through a flexible seal 11.

V Diaphragm spring 12 constantly urges the diaphragm in 33 61 Patented Feb. 7,1956

between the undersurface of the lever and a seating 21 inthe open mouth of lever housing 9. The arrangement is such that, upon rotation of cam 18, lever 13 is caused to oscillate, intermittently drawing stem 10 and the pump diaphragm in the direction to draw fuel into the pump. Spring 12 produces intervening discharge strokes, maintaining the desired constant discharge pressure. The length of the pump stroke varies in accordance with the work being done by the pump. a i

This type of mechanism, including the bearing shoe,

is better illustrated in the above mentioned co-pending application of James L. Edelen, which application describes how, during oscillation of lever 13, bearing-shoe slides back and forth along the lever under the impetus of the cam, as illustrated in broken lines in Fig.2;

' According to the present invention, the lever engaging bearing face of the shoe (Fig. 3) is provided with longitudinally relieved, central portions 22 which are interrupted by a boss-like land 23 surrounding an aperture 24 provided in the shoe for a securing rivet 25. The upper head of the" rivet seats in a countersink 26 in the curved, camengaging face 27 of the shoe. As clearly illustrated by the dot-and-dash line in Fig. 3, land 23 is located substantiah 1y wholly within the confines of slot 28 provided in'lever 13 for receiving the securing rivet. Thus, slot 28' co operates with'relieved, central portions not the lever engaging surface of the shoe to form continuous clearance portionsextending centrallyfrom end to end of both the lever and shoe bearing surfaces. This clearance area serves to form, at the sides thereof, laterally spaced, discrete, runner-like portions 29, represented in Fig. 3, and to completely eliminate the central bearing portions of these surfaces. The result of this is that the shoe is stably supported upon the lever along these runner-like portions so as to effectively eliminate rocking vibration between the parts.

These centrally relieved portions of the bearing surfaces also serve to reduce the extent of the bearing surfaces and, while concentrating the interacting forces,

substantially reduce the frictional resistance between the shoe and lever. This is important, in reducing vibration and chattering in that the sliding action of the shoe must be effected by application of forces from the cam to the projection of the shoe in a plane normal to its direction of sliding motion. For best action, this projection cannot be much greater than a shown in Fig. 2. It is, there fore, important that friction between the shoe and lever be reduced to a minimum.

I have found that by relieving the shoe and lever hear ing faces, as disclosed, the annoying whistling during operation is effectively eliminated.

The exact configuration of the bearing surfaces of the shoe and lever may be otherwise constructed, while retaining the runner-like engaging surfaces which prevent vibratory rocking. In Fig. 6, for instance, the web of lever 30 is depressed to form inwardly inclined side portions 31, provided with a slot 33 receiving the securing.

rivet 34. The lower bearing surface of the shoe 35,.

has oppositely inclined, laterally-spaced, runner-like beara appended claims is contemplated.

I claim: I I; 13 earn, follower shoe, having opposed bearing surfaces including a concave cam-engaging face and a lever engaging plane face centrally relieved substantially from end to end to form spaced, longitudinal bearing portions.

. 2., A; Wear; shoe for a cam follower; lever comprising;

opposite concave and plane faces for engaging, insurface contact, respectively; a, rotating cam, andan oscillating; lever, the lever engaging face. of, the shoe; having; longitudinal bearingprominences along the side. portions, thereof. V a

3; A, cam, follower; assembly comprising; anoscillating; levermember; and;v a cam; engaging shqe member longitudinally slidable thereon, the hearing,surfaces,of;saidimembers: being medially relieved: from; end to end and engaging alonglongitudinal; bearing portions; at opposite, sides; ofthe, longitudinal center line, thereof to minimizerela tive vibration of said members;

hen being substantially relieved, in restrictedv areas; to

provide; discrete bearingvportions rto, reduce; the friction, between said members. a .t

6. A cam follower; assembly comprising; a lever; mem

4 her and a shoe member; having bearing surfaces; capable of linearly'slidable relative movement, there being a longitudinal slot in the bearing surface of a first of said members and a securing element extending into said slot from the other member, there being a land in the bearing surface of said other member around said element, and within the limits of said slot and the central, longitudinal portion of said last-mentioned bearing surface, excluding said land, being relieved to form laterally spaced, runnerlike bearings between the portions. of said bearing surfaces beyond said slot.

7. A cam follower assembly as described in claim- 6 in which said boss is wholly within the limits of said slot in the assembly so that said slot and said relieved'portions form continuous clearance along the. longitudinal central portion of said bearing surfaces to eliminate vibratory rocking between said members.

References Cited in the file of this patent UNITED STATES PATENTS 292,077 Waggoner Jan. 15, 1884' 475,671, Conrady May 24', 1892' 1,225,726] Becker May 8, 1917 1,352,183, Conradson Sept. 7, 1920 1,372,408 Dyson Mar. 22', 1921 1,476,949. Cardullo Dec. 11', 1923' 1,524,486,, Marcalus Jan. 27, 1925 2,207,332 Paxton Y .Q, July 9, 1940 2,404,231 Harper July 16, 1946 2,419,316: Engemann- L. Apr. 22', 1947 2,508,557 Wood ..v ,r May 23, 1950' 2,654,266 Edelen Oct. 6', 1953 

